The invention relates to a process for purifying and decolorizing a phenyl ester salt. Phenyl ester salts are used as bleach activators in laundry detergents and other cleaning formulations.
Sodium hypochlorite and hydrogen peroxide are well known for their bleaching properties. As a bleaching agent in laundry detergents, hydrogen peroxide has the advantage of being safe to use with many fabric dyes. However, hydrogen peroxide bleaches are not effective at temperatures below 50xc2x0 C. This limits their use as most laundering is carried out at temperatures below about 40xc2x0 C. For this reason, various peroxyacids were developed as alternative bleaching agents for use in laundry detergents. The peroxyacids were generally found to be effective bleaching agents at the lower laundering temperatures. Because of their chemical instability and potential safety hazards, however, peroxyacids themselves are generally unsuitable for storage and handling.
Bleach activators were developed to address storage and handling concerns associated with peroxyacids. Bleach activators have the ability to hydrolyze under laundering conditions, effectively producing peroxyacids, even at lower temperatures, e.g. below 40xc2x0 C. Bleach activators have the further advantage of being stable when stored in solid form at room temperature. These properties permit the use of bleach activators in a variety of laundry detergents and other cleaning formulations.
An important class of bleach activators is phenyl ester salts. Formulas (I) and (II), below, depict the generic chemical formula of phenyl ester salts typically used as bleach activators: 
The various substituents and variables of the phenyl ester salts of formulas (I) and (II) are discussed below in the Detailed Description.
To be useful as a bleach activator, a phenyl ester salt must meet certain fitness-for-use parameters. The phenyl ester salt should have an acceptable perhydrolysis rate, that is the rate at which it reacts with bleach to form the corresponding peroxyacid. Perhydrolysis rate is a measure of the percentage of the phenyl ester salt that produces peroxyacid in a certain amount of time at a certain temperature. The peroxyacid must be produced quickly enough to be useful during the length of time and at the temperature of a typical wash cycle.
While it is important that phenyl ester salts employed in consumer detergent formulations have a high perhydrolysis rate, phenyl ester salts should also have acceptable levels of color and/or assay (or purity). These fitness-for-use parameters are also important and do not necessarily equate with a high perhydrolysis rate. A further problem is that the processes known in the art for making phenyl ester salts often produce products of highly variable quality requiring extensive purification or isolation procedures. Accordingly there exists a need for a process which purifies and decolorizes a phenyl ester salt to satisfy the fitness-for-use parameters of color, assay, and perhydrolysis rate.
The invention is a process for purifying and decolorizing a phenyl ester salt. The process combining a phenyl ester salt with a solvent to form a mixture. The phenyl ester salt is substantially insoluble in the solvent. The mixture is then stirred for a time sufficient to form a slurry. The phenyl ester salt is collected from the slurry and may then be dried. Drying the collected phenyl ester salt is an optional step. As another optional step, the collected phenyl ester salt may be recrystallized. The collected phenyl ester salt is then dissolved in a solvent to form a solution. The phenyl ester salt solution is decolorized and then spray dried to form a powder of the phenyl ester salt. As a result of the process, the phenyl ester salt powder has a higher purity and an improved color as compared to the starting phenyl ester salt. While each process step may be performed independently of the others, performing individual steps results in, at best, modest improvements in purity (or assay) and color. Practicing the process of the invention achieves the maximum benefits in purity and color and may also improve the phenyl ester salt""s perhydrolysis rate.